#include <atcoder/all>
#include <bits/stdc++.h>
#define rep(i, a, b) for (ll i = (ll)(a); i < (ll)(b); i++)
using namespace atcoder;
using namespace std;

typedef long long ll;

vector<int> make_primes(ll n) {
    vector<int> prime;
    vector<bool> is_prime(n + 1, true);
    is_prime[0] = is_prime[1] = false;
    for (ll i = 2; i <= n; i++) {
        if (is_prime[i]) {
            prime.push_back(i);
            for (ll j = i * 2; j <= n; j += i) {
                is_prime[j] = false;
            }
        }
    }
    return prime;
}

vector<int> ps;
vector<ll> v;

void solve() {
    ll n;
    cin >> n;
    if (n < v[0]) {
        cout << "-1\n";
        return;
    }
    auto it = upper_bound(v.begin(), v.end(), n);
    it--;
    cout << *it << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ps = make_primes(10000000);
    rep(i, 0, ps.size()) {
        if (ps[i + 1] - ps[i] == 2) {
            v.push_back((ll)ps[i + 1] * ps[i]);
        }
    }
    int t = 1;
    cin >> t;
    while (t--) {
        solve();
    }
}